I feel like my guy friend sees me as a little sister?

I've gotten close to this guy over the semester after we exchanged numbers at a party and i thought he may have been interested in me, and i even crashed at his house one weekend and he slept on the floor while i took his bed, nothing happened at all and i know he has hooked up with a decent amount of girls. When we first started talking it was a little bit flirty and he would always invite me to join him to study and stuff, but now its so platonic and casual.

I think sometimes I come off as kind of conservative and too nice, so I want to kind of "womanize" myself. I really like him, but I feel he sees me as a younger sister or something. I kind of have a baby face and I guess I'm kind of shy sometimes. I once asked if he thought so, and he said sometimes I seem nervous.